Aug. 6, J. c. WHITE 3,396,062 [NVE/WUR JAMES C. WHITE. Filed July 27, Sheets-Sheet 1 METHOD FOR MOLDING A COMPOSITE FOAMED ARTICLE

Transcription

1 Aug. 6, 1968 J. c. WHITE 3,396,062 METHOD FOR MOLDING A COMPOSITE FOAMED ARTICLE Filed July 27, Sheets-Sheet 1 im s..u@_ [NVE/WUR JAMES C. WHITE

2 Aug. 6, 1968 J. c. WHITE 3,396,062 METHOD FOR MOLDING A COMPOSITE FOAMED ARTICLE Filed July 27, Sheets-Sheet 2 f() C) C) VVE/WUR JAMES C. WHITE AZ'TÜRA/EYS

3 Unîted States Patent O c Ce 3,396,062 Patented Aug. 6, 1968 l 3,396,062 METHOD FOR MOLDING A COMPOSITE FOAMED ARTICLE James C. White, Lynniield, Mass., assignor to Sweetheart Plastics, Inc., Wilmington, Del., a corporation of Maryland Filed July 27, 1964, Ser. No. 385, Claims. (Cl ) ABSTRACT 0F THE DISCLOSURE A method of thermoforming foam plastic insulated articles is provided where at least one layer of a cellular foamed thermoplastic material is heated by contact heat ing and the heat of said contact heating is used in the thermoforming molding step. Preferably at least one sheet of foam plastic is used in combination with a solid thermo plastic liner and contact heating is used to derive the heat necessary for molding. This invention relates to thermoforming and more par ticularly to thenmoform'ing methods for fabricating insu lated articles having at least one layer of a cellular foamed thermoplastic material. The use of disposable plastic food and beverage con tainers has become widespread in recent years due at least in part to the rapid increase in the market for such products and to the inherent advantages of plastics as opposed to» previously used paper products. However, problems have been encountered in economically manu facturing plastic containers such as cups for use in hold ing hot beverages. Thin walled cups often allow undesir able heat transfer to the hand of a user while thick walled cups are economically prohibitive. Thus, the art has turned to the consideration of cellular foamed thermo plastic materials for use in hot or cold container appli cations in an effort to insulate these containers. Some cellular foamed cups now on the market are individually molded of foamable bead material. Such cups do have good insulating properties but suffer the dis advantages of relatively high manufacturing cost and relatively large stacking space requirements. Close stack ing or nesting of such cups is diñicult to achieve due to inherent wall thickness requirements of foamable bead molded cups. Thus, some thought has -been given to the use of thin low density thermoplastic foamed sheets which can be formed by thermoforming techniques into cups and the like. Normally such sheets are not sufficiently self-supporting during molding. Thin foam sheets tend to tear or undergo cellular collapse after heating. There fore, laminates 0f foamed sheet with solid or high den sity layers or sheets have been suggested. When such laminated sheets are molded by conven tional thermoforming techniques such as Ivacuum form ing, problems often arise. In some cases, the foam sheet delaminates and/or blisters from the high density layers. Collapse of the cellular structure of the foam often occurs when using normal thermoforming techniques. Nonuni form thickness of foam layers in completed cups also occurs with relatively high frequency when using normal methods. A further problem is encountered due to the relatively high cost of cellular foamed sheet materials, and the waste factor encountered in conventional single or plural station vacuum forming or other thermoforming methods. Thus, when a laminate comprising a high density liner and a cellular foamed sheet is passed into a multi-cavity vacuum thermoforming machine, only portions of the laminate corresponding with the cavities are formed into usable shapes. Areas between the formed shapes become Ul lo waste material areas increasing the cost of each shape formed. Similarly, in single cavity molding waste areas of foam may extend beyond the cavity opening area. It has now been found that the use of contact heating of a foam laminate to bring the laminate up to forming temperature is important in the fabrication of thin walled insulated foam laminate containers made by thermoform ing methods. In addition, the use of preselected foam layer areas on a plastic backer or liner sheet consider ably reduces over all cost in making thin walled con tainers comprising at least one layer of thermoplastic foam material. It is an important object of this invention to provide a practical method of molding containers such as cups from a sandwich comprising a layer of low density cellu lar foamed thermoplastic material. It is another object of this invention to provide a meth od in accordance with the preceding object which can be economically carried out with substantially conventional equipment to provide containers such as hot beverage cups which possess the necessary insulating properties so that they can be handled comfortably even when filled with beverages at temperatures as high as 212 F. This temperature is well above the normal 205 F. tempera ture of hot beverages served over the counter and 190 F. temperature of hot beverages dispensed from vending machines. It is still another object of this invention to provide a highly economical method of forming plural layered cellular foam insulated containers. Still another important object of this invention 'is to provide a method of molding inexpensive containers comprising plural layers of cellular foamed material which have been joined together. According to the invention, a molded article such as a hot beverage container is formed from a sandwich comprising at least one layer of cellular foamed thermo plastic material on a liner or backer sheet. The sandwich has an upper surface and a lower surface. An area of the upper surface is engaged with a ñrst contact heating means while substantially simultaneously engaging an area of the lower surface of the sandwich opposite the upper surface with a second contact heating means thereby confining a portion of the sandwich between the two heating means. The upper and lower surface areas are then heated by conduction to the forming temperature Of the sandwich while it is confined, and the Sandwich is subsequently thermoformed utilizing the heat derived from the above heating steps. Thermoforming such as plug assist pressure molding can be used and the sandwich can comprise two or more layers of cellular foamed thermoplastic material and a thin sheet of comparatively high density or solid thermo plastic material compatible with the foamed layers. It has been found that the use of two layers of cellu lar thermoplastic material provides slightly better insu lating properties to the completed container as opposed to the use of a single cellular foamed layer having a thickness substantially equal to the combined thickness of the t-wo layers previously mentioned. Preferably a plurality of containers or cups are formed from a single sandwich using conventional pressure form ing molding cavities distributed at spaced intervals over the sandwich as is known. The sandwich may comprise a single sheet of cellular foamed thermoplastic material and a high density liner or various combinations of plural cellular foamed sheets and plural liners. In some cases, the liner may be eliminated although the mechanical strength of unlined containers is reduced. An improvement of the basic method of this invention comprises the use of a sandwich having a backer or liner which acts as a carrier sheet on which are positioned pre

4 3,396,062 3 formed layers in spaced defined areas comprising cellu lar foamed thermoplastic `material with the defined areas and their spacing conforming and corresponding to ori fice openings of a bank of spaced mold cavities aligned for molding of a plurality of articles from the sandwich. Similarly, when single cavities are used, the foamed ther moplastic areas on the liner preferably conform to the cavity opening size while the liner is greater in surface area than the cavity opening. The use of spaced areas can enable savings as high as 50% of over all cost of the relatively expensive cellular thermoplastic material. The use of a carrier sheet and a foam layer sandwich provides advantages even when using single cavities or molds to form laminated articles. These and other objects and features of this invention along with its incident advantages will be better under stood and appreciated from the following detailed de scription read in connection with the accompanying draw ings, in which: FIG. 1 is a diagrammatic showing»of an apparatus for carrying out a method of this invention; FIGS. 2-5 are cross-sectional views through beverage cups made in accordance with the teachings of this in vention; FIG. 6 is a top plan view of a sandwich for use in thermoforming of insulated containers; FIG. 7 is a diagrammatic showing of a»method for forming cups from a sandwich as shown in the embodi ment of FIG. 6; and FIG. `8 is a top plan view of a sandwich for use in a 30 single cavity molding method. Turning now to an embodiment of the method of this invention, FIG. l illustrates an aligned feeding Zone 10, contact heating zone 11, and molding zone 12. Sheets of thermoplastic material to be laminated and/or molded in accordance with this invention are fed from the feed ing zone 10 `between an idler roller arrangement 17, 17a to form a sandwich 16 which passes through the heating zone 11 and is heated by conduction over upper and lower surfaces by contact heaters 18 and 19. The sandwich is then passed into a plurality of conventional molds such as plug assist air pressure molds one of which is diagram matically illustrated in the molding section 12 and molded into beverage cups. The feeding zone 10 preferably contains a ñrst roll 13 of solid thermoplastic sheet material which acts as a liner or backer. Rolls 14 and 15 preferably contain foamed cellular thermoplastic sheet material. Although two rolls 14 and 1S are shown Vfor purposes of illustration, it should be understood that a single roll can be used in the same, apparatus. Sheets taken from rolls 13, 14 and 15 are passed between idler rollers 17 and 17a, which are un heated and preferably position the sheets in a sandwich 16 without laminating the sheets one to another or sub stantially compressing the sheets. Preferably rollers 18 and 18a act as pull rollers to carry the sandwich through the processing zones at selected time intervals. In some cases rollers 17 and 17a may be power driven. Heating is accomplished in the heating section 11 by means of an upper contact heater 18 and a lower contact 60 heater 19. Each of the contact heaters 18 and 19 are preferably substantially identical and only heater 18 will be more fully described. Heater 18 preferably comprises a cylindrical piston head 18a having a lower circular sur face thereof 21 coated with a release medium such as a thin layer of Teñon. The piston head is reciprocated into and out of engagement with an upper surface of the sandwich 16 by a stationary air cylinder 20 at selected time intervals simultaneously with contact of the lower contact heater 19 with a lower surface of the sandwich 16 opposed to the upper sandwich being contacted by heater 18. Thus, surface to surface contact is made with both upper and lower surface areas of the sandwich 'While the upper and lower piston heads apply a positive pres sure to confine the sandwich therebetween thus pre ' 4 venting uneven expansion of the surfaces confined. Pref erably suñ icient heat and pressure is imparted to the sand wich to heat seal or laminate the layers to each other. It is also possible to carry out` the actual heat sealing of the sandwich layers to form a laminate in the thermoform ing mold 24 during the molding step without the need for additional heating. It is found that in some cases it is not necessary to heat seal the entire contacting surfaces of the layers, but spot sealing of portions of the contact ing surfaces is suiiicient to produce acceptable molded products. Although only one contact heater pair is shown in FIG. l, it should be understood that this invention contem plates the use of a bank of heaters arranged Iboth longi tudinally and transversely of the sandwich 16. Each of the heaters heats a surface area on the sandwich 16 cor responding to a mold cavity in the molding section. If the lmolding cycle is shorter than the heating time for a specific thermoplastic sandwich, it is possible to provide for multiple heating steps -by arranging two or more con tact heaters along the line of the elongated sandwich 16. Thus, heating can be accomplished partially by a first contact heater and completed by a second or subsequent contact heater with the intermittent regular step advance ment of the sandwich 16 being limited lonly by the mold ing cycle time required lfor molding an article. After passing through the heating zone 11, the sand wich 16 is drawn into the molding section 12 with each heated area being placed adjacent an opening of a mold ing cavity one of lwhich is diagrammatically illustrated at 24. The preferred mold cavity 24 is a conventional air pressure molding cavity having suitable vents 25 and a plug assist 26. The heated area of the sandwich shown in FIG. 1 by the dotted portion 29 may expand slightly as it passes from the heating zone 11 to its position shown in FIG. 1 due to slight expansion of the foamed sheets. At the mold cavity 24 the sandwich is clamped by a conventional clamping ring 27 and molded into the shape of the cup shown in FIG. 2 utilizing the heat imparted by the contact heaters. Suitable rim or flange forming de vices (not shown) can be used to simultaneously form rims in the molded cups. Cups formed in molds such as 24 are removed by an air blow ofi, mechanical or other conventional means and the sandwich 16 is then advanced. As mentioned previously with regard to the heating zone, plural molding cavities are preferably positioned both transversely and Álongitudinally of the sandwich in posi tions corresponding to the positions of the heaters, to pro vide for plural cup formation from selected areas of the sandwich 16. The thermoplastic materials used in the method of this invention preferably comprise polystyrene such as impact polystyrene. However, other known thermoplastic mate rials may be used including but not limited to vinyl poly mers, acetates such as cellulose acetate and polyethylene. Preferably, both the solid carried sheet or liner 13 and the cellular foam thermoplastic sheets 14 and 15 are of the same thermoplastic material. However, in some cases different materials can be used for the different sheets or layers of the sandwich 16 formed by the method of this invention. When polystyrene or impact polystyrenes are used in the method of this invention, it is preferred that the liner 13 have a thickness within the broad range of 5 to 25 mil and a range of 18 to 23 mil liner is found to be most suitable. The total foam layer thickness is preferably with in the range of 10 to 120 mil with an optimum range of foam layer thickness of from 30 to 90 mil. While thicker materials may be used, this may defeat the purpose of obtaining a light weight, well insulated, deep draw, nest able cup or article. When articles other than polystyrene containing cups are to be formed the over all thickness of 145 mil can vary considerably. Similarly, if no liner is used and a foamed layer comprising one or more sheets

5 5 of polystyrene is employed, the thickness of the foamed layer can vary considerably. The heaters 18 and 19 preferably exert pressures of from 5 to 25 p.s.i. on the areas confined between them. Preferably the contact heater touching the lower surface of the sandwich 16 in contact with the solid thermoplastic is heated to a temperature of from 265 F. to 350 F. while the upper contact heater 18 adjacent the foam sur face is heated to a temperature of from 320 F. to 375 F. In most cases it is found to be preferable to heat the foamed layer to a lesser degree than the solid thermo plastic layer. While the heater 18 is preferably heated to a higher temperature than heater 19 the foam layer itself is heated to a lesser extent than the solid layer due to the lower heat transmission properties of foam. Heat is preferably applied by the contact heaters for a period from 21/2 seconds to l2 seconds. Molding temperatures in the range of 260 F. to 300 F are preferable. Preferably the density of the polystyrene used in the foam sheets is in the range of from about 4 to l5 pounds per cubic foot and the density of the solid sheet is from about 20 pounds per cubic foot to about 65 pounds per cubic foot. When a single sheet of foam is used without a solid liner, its density is preferably in the range of from 15 to 30 pounds per cubic foot. Lower densities are nor mally preferred in order to obtain articles having low unit weights. The heat applied by the Contact heaters is preferably the heat used to form or mold the articles thus the spacing between the contact heating section and the molding sec tion 12 is small. The molding cycle is preferably the same as the heating time although variations can be used since the contact heaters are reciprocal toward and away from the sheet and may be removed from the sandwich during portions of the molding cycle if desired. While each of the ranges given above are preferred, it will be obvious that variations may be made depending upon the over all thickness of the sandwich or single foam layer, particular material being treated, and the density of the foam sheets. The ranges given are useful in forming insulated cups from polystyrene materials but will vary when forming other articles from other materials. In a speciñc example of this invention, shown in FIG. 1, roll 13 is a sheet of Monsanto LLlS impact polystyrene material having a thickness of inch and rolls 14 and 15 are each sheets of cellular foamed polystyrene each having a thickness of 0.45 inch and a density of 6.5 pounds. A total cycle time of 6 seconds is employed for both the heater section and the molding section. Each con tact heater has a piston head with a thin Teflon coating and a lower surface area of approximately 18.5 square inches. A heater temperature of 350 F. is used for the upper heaters 1S contacting the foam and a temperature of 320 F. is used for the lower heaters 19. Six pairs of heaters ranged in two rows transversely of the sandwich are used with corresponding six molding cavities. Heater pressures of 18 pounds per square inch are exerted between each upper and lower piston head and the heated sand wich is advanced from the heating section to the molding section within 0.5 second of heating. Each molding cavity is a cup cavity for molding a 7 ounce cup having a height of 35/16 inches and a rim diameter of 2.9 inches. Each cavity is maintained at 85 F. A plug 26 and air pressure of 100 p.s.i. are used. I_aminated cups shown in FIG. 2 are formed with a solid liner 13, and foam layers 14 and 15. These cups are uniformly produced with substantially even surface foam outside walls and with all `layers sub stantially uniformly heat sealed together over their con tacting surfaces. The resultant cups formed could be held in the hand of a user for over 180 seconds when filled with a liquid having a temperature of 170 F. In a second speciñc example of this invention, the ñrst example was repeated. However, rolls 14 and 15 were re placed with a single roll 14 of polystyrene insulation hav ing a density of 7.5 pounds, and a thickness of approxi 3,396, mately 0.45 inch. The insulating value of the molded cup obtained as shown in FIG. 3 was lower than that obtained in the molded cup of FIG. 2 as previously described. For example, when filled with water having a temperature of 170 F., such cups provided adequate insulation to the hand of the user for at least 65 seconds. In a third speciñc example of this invention, the contact heating section 11 was replaced with radiant heaters spaced approximately six inches from the surfaces of the sandwich 16. All other conditions given ín the first exam ple were followed. The radiant heaters were sufficient to heat the upper surface of the sandwich 16 to 345 F. and the lower surface to 320 F. Resultant cups formed in ac cordance with this third example showed severe blistering of the insulation layer and extremely poor insulation mak ing them undesirable for use as hot drink containers. In alternate embodiments of the method of this inven tion, the number of foamed sheets and solid thermoplastic sheets are varied in the method described with respect to FIG. 1 to produce cups as shown in FIGS. 4 and 5. The cup shown in FIG. 4 is formed of two laminated layers of foamed thermoplastic material 30 and 31 without the use of a backer or liner such as 15. FIG. 5 illustrates the use of an inner foam layer 34, central foam layer 36 and outer layer 35 of a solid liner material. In still another modification.of this invention, the sand wich 16 may be laminated by the use of solvents and/or heat previous to entrance into the contact heating zone. While this is not necessary, it may be desired for ease of handling. Where desired, the sandwich 16 may be pre laminated in accordance with conventional methods. In some cases the lamination occurs in the mold 24 during the forming operation. In some cases, both the foam sheets and the liner sheets or any one of them may be extruded directly from an extruder to the contact heating zone without ñrst rolling these materials as shown. Turning now to an improvement of the invention, and with particular reference to FIG. 6, a schematic repre sentation of the invention is shown with a liner roll 13 of solid thermoplastic sheet material as previously de scribed mounted for passage of the sheet through a foam applying Zone 42, heating zone 43 and molding zone 12. In this embodiment, rather than applying the cellular foarned thermoplastic material in elongated sheet form as described in FIG. 1, the cellular foamed thermoplastic material is applied to the liner sheet 13 in the form of discs 41 by the use of any suitable disc discharge apparatus 42 or by hand. Each disc 41 has an outer conñguration slightly greater than the opening of the mold cavity 24. As best shown in FIG. 7, a plurality of discs 41 are ap plied to the sheet 15 corresponding in number and posi~ tion to the number and position of the molding cavities used and the heating means used if contact heaters are employed. Plural discs may be used to form a layer of plural thickness 4of foam as well as a liner of foam to provide various combination sandwiches and resulting cups as previously described. The heaters 43a and 43b are preferably contact heaters as described with reference to contact heaters 18 and 19 of FIG. 1. However, cost saving advantages are obtained from the use of discs or predetermined areas of foam, even if radiant heating is used. Heating by radiant heat rather than conduction does result in certain problems as previously pointed out. Molding Zone 12 is a substantial duplicate of that de scribed with reference to FIG. l. The discs 41 are lami nated either during the heating step or the molding step as previously described although they may be applied with a solvent or prelaminated to the liner 15 before reach ing the heater. In some cases, it is possible to position the discs on the underside of the liner by the use of solvents or heat previous to molding so that a downwardly open ing mold cavity can be employed. The specific times, tem peratures, materials and sequence of operation described

6 8,396,062 8 with respect to FIG. l is preferably employed in this em While specific preferred times, temperatures, pressures bodiment of the invention. and other parameters have been described particularly for As best shown in FIG. 7, since discs 41 cover substan use with deep draw insulated cups preferably formed from tially only those portions or areas of the liner 13 which polystyrene materials, these parameters can vary greatly are formed during the molding operation, a considerable Ut with other materials and when forming other molded reduction in the amount of cellular foamed thermoplastic articles. material used is possible. Since the cellular foamed thermo From the foregoing description it will -be appreciated plastic material is a relatively high cost raw material, over that numerous modifications may be made of the inven all costs may be considerably reduced. tion without departing from the spirit of the invention. FIG. 8 illustrates a liner 13 made of a solid thermo~ Because numerous modifications may be made of this plastic sheet having a rectangular outer configuration and invention, it is not intended to limit the breadth of this a single disc 41 of cellular foamed thermoplastic material invention to the embodiments illustrated and described. lying thereover. This arrangement can be used in a single Rather, it is intended that the breadth of this invention cavity molding process. It is preferred that the area and be determined by the appended claims and their equiva outer configuration of the disc be less than the surface lents. area and outer configuration of the liner to provide cost What is claimed is: savings. 1. A method of forming a molded article from a layer The disc 41 of FIG. 8 may be large enough to be of foamed thermoplastic material having an upper sur clamped at its edges by a clamping ring such as 27 during face and a lower surface, molding. Alternatively, the disc 41 can have a surface said method comprising, area and outer configuration smaller than the inner diam contacting an area of said upper surface with a first eter of the clamping ring or other clamping means and heating means while substantially simultaneously preferably substantially equal to the area and diameter contacting an area of said lower surface opposite of the mold cavity opening in which it is formed. In some said upper surface with a second heating means cases the disc is of smaller diameter than the cavity open whereby a portion of said layer is confined between ing. When the disc 41 is not clamped during molding it said upper and lower heating means, is necessarily attached to the liner 13 at least at certain heating said upper and lower surface areas to the spots such as near its outer edges, prior to molding. The forming temperature of said layer while said sheet edge attachment can be made by spot heat sealing or by is confined and subsequently removing `said sheet the use.of adhesives. 30 from said upper and lower heating means and forlm The method and conditions previously described with ing said foamed layer employing heat derived from relation of FIG. 6 are preferably employed. However, said heating step. since a single cavity is used, no continuous elongated sand 2. A method in accordance with the method of claim wich need be employed and the sandwich 16 of FIG. 8 1 wherein said sheet is confined between said upper and can be either jig or hand positioned between the heaters 35 lower heating means under pressure of 5 to 25 p.s.i. and in the mold A method in accordance with the method of claim 1 Even if the disc 41 is not clamped during molding, the and further comprising expanding said foamed layer by liner 13 is clamped and acts as a carrier for the disc during said heat derived from heating step before said forming shaping. Cups such as shown in FIG. 3 can be formed step. economically in single cavity molds by the use of sand A method of forming a molded article from a layer wich 16' of FIG. 8. of foamed thermoplastic material in accordance with the It should be understood that the disc 41 of FIG. 6 can method of claim 1 wherein said foamed thermoplastic have an outer diameter smaller than the clamping diam material is moved along a path and contacted by said eter of the clamping means 27 and conversely the disc 41 upper and lower heating means at a first position in said of sandwich 16l can have an outer diameter larger than path, the clamping diameter of clamping means 27. Thus, it is and said forming is carried out at a second position possible to clamp or retain both the liner and the foamed along said path. disc or to clamp or retain only the liner during the molding 5. A method of molding a composite sheet comprising steps. a first layer of low density foamed thermoplastic mate In some cases the solid liner 13 of FIG. 8 can be in the rial and an adjacent sheet of a thermoplastic liner, form of an elongated sheet with a plurality of discs 41 said composite sheet having an upper surface and a arranged thereon in an elongated line to permit continuous lower surface, heating and subsequent feeding to a single molding cavity. said method comprising the steps of contacting an area While specific embodiments of this invention have been of said upper surface with a first contact heating shown and described, it will be obvious to those skilled in means while substantially simultaneously contacting the art that many variations thereof are possible. For ex an area of said lower surface opposite said upper ample, while thermoforming such as pressure molding is surface with a second contact heating means whereby preferred for use in this invention, vacuum forming, air a portion of said composite sheet is confined between slip forming and match folding may also be employed. and in surface to surface contact with said upper The use.of contact heating in a foam thermoforming 60 and lower heating means, process is an important step in the method of this inven conduction heating said confined upper and lower sur tion. In its broadest aspect the invention contemplates con face areas to at least the molding temperature of duction heating of a cellular foamed thermoplastic sheet said composite sheet and subsequently, removing said to bring the sheet to its molding temperature. In addition, composite sheet from said upper and lower heating the use of discs or other configurations of foamed mate means and rial conforming to slightly smaller or slightly larger than molding said composite sheet heated areas employing mold cavities used is also of'great importance in reduc heat derived from said heating step. ing over all expense. It is preferred to produce cups having foam outer layers 6. A method in accordance with the method of claim 5 and a solid inner liner to enhance printability, reduce in wherein a surface of said first layer is heated to a tem 70 ner wall staining, improve over all outer appearance and perature of from 320 F. to 375 F. and a surface of improve ease of rimming. However, it is also possible to said sheet is heated to a temperature of 265 F. to 350 F. reverse the order of the sheets shown in FIG. 1 to produce 7. A method in accordance with the _method of claim 5 cups having an inner wall of foam and an outer solid wherein said layer and said sheet are laminated together thermoplastic wall. -' KI Ch prior to said contact heating step.

7 8. A method in accordance with the method of claim 5 wherein said temperature is maintained for a sutîicient period of time to uniformly bond said firs-t layer to said sheet without collapsing cells of said foam layer. 9. A method in accordance with the method of claim 6 wherein said foamed layer comprises polystyrene foam having a density of from 4 to 15 pounds per cubic foot and a thickness of from 10 to 120 mils, and said thermoplastic liner having a thickness of from 5 to 25 mils. 10. A method in accordance with claim 9 wherein said thermoplastic sheet comprises a solid thermoplastic sheet having a thickness of from 8 to 23 mils and said foamed layer having a thickness of from 30 to 90 mils. 11. A method in accordance with the method of claim 5 wherein said foamed layer has a density of from 4 to 15 pounds per cubic foot. 12. A method of forming thermoplastic articles com prising, forming a sandwich comprising a first layer of foamed thermoplastic material, a second layer of foamed thermoplastic _material and a sheet of a solid thermo plastic liner with said sandwich having a first outer surface provided by said first layer and a second outer surface provided =by said solid thermoplastic liner, contacting a selected area of said iirst surface with a first contact heating means and contacting a selected area of said second surface with a second contact heating means, heating said first and second surfaces through said con tact heating means to at least the molding tempera ture thereof, and subsequently, thermoforming said selected areas utilizing heat derived from said heating of said first and second surfaces. 13. A method in accordance with claim 12 wherein said first surface is heated to a temperature within the range of from 320 F. to 375 F. and said second surface is heated to a temperature of from 265 F. to 320 F. 14. A method in accordance with the method of claim 13 wherein said foam layers have a combined thickness in the range of from 10 to 120 mils and said heating is carried out while confining 'said selected areas a-t a pres sure in the range of from 5 to 25 p.s.i. 15. A method in accordance with the method of claim 13 wherein said sandwich areas are confined during said heating. 16. A method in accordance with the method of claim 15 wherein said foamed layers have a density within the range of from 4 to 15 pounds per cubic foot. 17. In a method of forming an insulating container from a composite sheet, the steps 0f forming said com posite sheet with at least two adjacent layers of foamed thermoplastic material, contact heating a plurality of distinct selected areas of said composite sheet to at least the molding tem perature of said composite sheet while confining said areas and subsequently releasing said composite sheet and thermoforming said selected areas of said shee-t into said insulated container utilizing the heat de rived from said contact heating. 18. The method of claim 17 wherein said composite sheet further includes a solid thermoplastic line-r and said compo-site sheet has a thickness no greater than 145 mils. 19. In a method of forming a thermoplastic article from a composite sheet comprising at least one outer layer of a foamed thermoplastic material the improvement comprising substantially simultaneously contact heating opposing surfaces of said composite sheet to heat a selected area of said composite sheet to the molding temperature thereof while said selected area is confined and subsequently releasing said composite sheet and subsequently 3,396, thermoforming said area into a thermoplastic article utilizing heat derived by said contact heating. 20. The improvement of claim 19 wherein said op posed surfaces are heated to different temperatures. 21. A method of economically producing foam lami nated molded containers having a first foamed thermo plastic layer and a second thermoplastic layer, said method comprising advancing an elongated sheet of said thermoplastic material toward a plurality of spaced thermoforming molding cavities, said cavities each deñning predetermined cavity mouth dimen sions, forming a composite sheet by positioning a plurality of foamed thermoplastic shapes on spaced areas of said elongated sheets with said areas corresponding to spacing of said plurality of molding cavities, said lshapes each defining an outer perimeter closely conforming to the dimensions of corresponding _molding cavity mouth dimensions, heating `said shapes and spaced areas to molding tem perature and thermoforming said composite sheet at said spaced areas to produce said foam laminated containers. 22. A method in accordance with the method of claim 21 wherein said shapes comprise fiat discs. 23. A method in accordance with the method of claim 22 -wherein at least two of said shapes are positioned over each of Said spaced areas. 24. A method in accordance with the method of claim 21 wherein said composite sheet is heated at said areas by conduction and said thermoforming is carried out utilizing said heating by conduction. 25. A method of economically producing a cellular foamed thermoplastic article comprising, positioning a layer of cellular foamed thermoplastic material having a predetermined surface area over a sheet of thermoplastic material having a surface area larger than said predetermined surface area to form a composite sheet, heating said layer and said sheet to the molding tem perature of said composite sheet, positioning said composite sheet in operative relation ship with a molding cavity having an opening de fining an area substantially corresponding to said predetermined area and molding said composite sheet into said article utilizing heat derived from 'said heating step. 26. A method in accordance with the method of claim 2S wherein said sheet is clamped about said molding cavity opening during said molding, and said layer and said sheet are joined to each other prior to said molding. 27. A method in accordance with claim 25 wherein said predetermined area of said layer is Áslightly greater than said cavity opening area and covers said cavity opening area, ' and said sheet and an outer edge of said layer are =both clamped about said molding cavity opening during said molding. 28. A method in accordance with the method of claim 25 wherein said heating is carried out by contact heating of said composite sheet over said predetermined surface area. References Cited UNITED STATES PATENTS ' 3,199,757 8/ 1965 McConnell ,203,611 8/1965 Anderson et a l.5 3,237,834 3/1966 Davis et al 229~l.5 2,120,328 6/1938 Ferngren ,702,411 2/ 1955 Wins-tead XR 2,958,898 11/1960 Voumard et al. 3,238,565 3/1966 Jacobs (Otherlreferences on following page)

8 1,752,402 2,893,877 2,979,246 3,039,911 3,104,192 3,126,139 3,137,747 3,141,595 UNITED 4/1930 7/1950 4/1961 6/1962 9/1963 '3/1964 6/1964 7/ STATES PATENTS Tomec et al `XR Nickolls XR Liebeskind XR FOX `XR Hacklander XR Schechter XR Kline XR Edwards... -_' $896,062 3,159,698 3,211,814 3,220,902 3,234,065 V3,260,781 12/ / /1965 2/1966 7/ Suh et al Kohrn et al Edwards XR Best XR Lux et a JAMES A. SEIDLECK, Primary Examiner. PHILIP E. ANDERSON, Assistant Examiner.